Process for the production of sheets or strips with oriented magnetic properties from silicon and/or aluminum containing iron alloys



United States Patent PROCESS FOR THE PRODUCTION OF SHEETS OR STRIPS WITH ORIENTED MAGNETIC PROPER- TIES FROM SILICON .AND/OR ALUMINUM CONTAINING IRON ALLOYS V Hans-Eberhard Miibius, Altena, Westphalia, Germany, assignor to Vereinigte Deutsche Metallwerlre 'Aktreugesellschaft, Frankfurt am Main Heddernh'erm, Germany a No Drawing. Filed Dec. 10, 1957, Ser. No. 701,712

Claims priority, application Germany Feb. 16, 1957 8 Claims. (Cl. 148-111) The present invention relates to a process for the treatment of strips or sheets of silicon and/or aluminum containing iron alloys whereby a' marked cube texture is achieved, that is, a texture having a large number of well oriented crystals with the cu-be face, (100) in. the Miller indices, parallel to the plane'offthe strip 'or sheet and the cube edge, [001] in the Miller indices, parallel and at right angles to the rolling direction.

The single crystal of the usual soft magnetic iron containing 2.5 to 4.5% of'siliconfis anisotropic inns magnetic properties, It is easiest to .jnrag'netize in the direction of the cube edge [100], andis more difficult to magnetize in the direction of the face diagonal [110] and is most difficult to magnetize the direction of the space diagonal [111]. i 1. 1

By the use of two fold cold rolling with an interposed intermediate anneal and a final anneal at high temperatures, it has been possible to obtain a recrystallization texture from: polycrystalline material which is described as (110) [001] texture and in general is referred to as Goss texture (see US. Patent 1,965,559). I This texture has the advantage that it is easily magnetized in the rolling direction. On the other hand,' it1has unfavorable magnetic properties in the direction'transverse to'thc E rolling direction. The cube texture, that is, the (100) [001] texture, however, is sought after. as itiseasy to magnetize both in the direction ofr'olli'ng' andin the direction transverse thereto.

In order to produce sheets for use in electrical apparatus, motors and transformers which-have favorable magnetic properties in two directions which are perpendicular to each other, it has already been recommended to roll the hot rolled sheets sequentially at right angles to each other (cross-rolling). The deformation texture thus obtained can be retained by careful recrystallization. The directions of easiest magnetizability in the sheets obtained with such cross-rolling process are in the two directions which are at a angle to the rolling directions.

As a consequence, it is possible to cut out a core' sheet from such sheets which have an approximate (100). [001] texture.

It furthermore has been proposed to turn the sheet at a to 70 angle to the original rolling direction in the last cold rolling passes (diagonal rolling). This renders it possible to obtain a recrystallization texture which is preferentially magnetizable both parallel and transverse to the rolling direction. The crossand diagonal-rolling procedures, as is well known, are very time consuming and furthermore require much experience. Furthermore, such procedures provide many difficulties and they cannot be used for the production of strip material. As a consequence, the

crossand diagonal-rolling procedures are hardly ever v cold rolling conditions; 11 addition,

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it has also been found desirable to provide "a 'specialageing treatment between the last cold rolling treatment and the final recrystallization heat treatment.

The silicon content in the case of silicon iron alloys must be between 0.5 to 2.5%, the aluminum content in the case of aluminum iron alloys must be between 0.5 and 2.0% and in the case of silicon-aluminum iron alloys' the sum of the quantities of silicon and aluminum should be between 0.5 and 2.5%.

The alloys treated according to the invention, as is customary in high quality alloys for magnetic purposes, may contain a small metalloid content for instance sulfur up to 0.03%, phosphorus up to 0.03% and carbon up to 0.05%. Ifthe starting alloy does not have a sufliciently low metalloid content after the customary hot rolling treatment it should be given a refining anneal under hydrog'en or vacuum in order to reduce its metalloid content to the necessary degree before the cold rolling.

The alloys employed according to the invention can, if desired, also contain nickel in small quantities, for example, up to'1%, suchfas in amounts of 0.11 The nickel can also be wholly or partly replaced 'by one or more'other metals, such as chromium, cobalt, manganese, copper, zinc and vanadium, whose atom diameter is as close as possible to that of iron. p

The cold rolling condition which must bev maintained in the process according to the invention resides in the selection of the degree of reduction in the cold rolling. When multiple stage cold rolling is employed with intermediate anneals, the deformation degree or degree of reduction of the second to last deformation is of decisive significance It should be greater than and preferably should be about to The last degree of deformation can be lower. In simpleQsingle stage cold rolling, i.'e., Without intermediate annealing, it is necessary to effect a very high deformation degree as it was found generally the higher it is the more marked the cube texture obtained. However, it should not exceed and'preferably is between 70 and 90%. Inaddition, it was found according to the invention that the number of passes employed in the cold rolling is not insignificant. -It was unexpectedly found that the numberof passes employed in multiple stage cold rolling (with intermediate anneals) should be between rather narrow limits. For the process according to the invention it is important that the deformation is effected with as small a num-her .of passes as possible aswith increasing number of passes the cube texture is formed increasingly more weakly. It is therefore preferable that the number of passes in the last'lcold rolling stage and also many second to last stage,.if possible, should not exceed 10 and advantageously .the number of passes is selected between '2 and ,8. .-In the process according to the invention the cold rolling. can be effected in the same direction, or reversing or partly: in the same direction and partly reversing. However, rolling in the same direction in general produces a more marked cube texture.

The quality of the grain orientation obtained upon the final anneal inthe strips or sheets which have been cold rolled in the above described manner, however, is variable. As a consequence, a relatively widespread of wattage losses result. I

Consequently, it has been found. advisable according to the invention to employ a further measure to insure the production of a well oriented'cube texture, namely, an ageing step.- The ageing expediently is carried out immediately after the last cold rolling and can be carried out either at room temperature or at elevatedtemperature.

is of advantage to age atas low temperatures as possible, as at high temperatures the phenomena which favor- 3 ablyafiect-the texture proceed so rapidly that they cannot be controlled with certainty. It was therefore found advantageous to select a temperature not over 300 C., preferably not over 250 C.,' for such ageing treatment. With an ageing temperature of 100 C. an ageing period of 1 to 10 hours, preferably 3m 6 hours, sufiices. When ageing is carried out at room temperature,considerably longer ageing periods come into consideration which may stretch over several days, preferably 2 to 10 days.

In the event that the final anneal is not carriedout immediately after the ageing, it has been found desirable to cool the sheets or strips to about C. or lower and to maintain them at; such low temperature until the final anneal is effected. Also, in some instances it may be advisable to maintain the cold rolled stock at such low temperatures before the ageing treatment if it is not convenient to carry out the ageing treatment immediately after the cold rolling.

The cold rolled strip or sheet material can, for example, be aged by letting it stand after completion of the cold rolling at temperatures between 20 and 35 C. for 2 to 10 days and only thereafter subjecting it to the final anneal. It is also possible, for example, to place the sheet or strip material after completion of the cold rolling directly into the oven which is to be. employed for the final anneal while still warmfrorn aprevious anneal and to wait for a certain period of time dependent upon the temperature of the warm oven before beginning the heating for the final anneal or an anneal preceding such final anneal. I

The strips or sheets produced by the process according to the invention preferably have a thickness of 0.2 to 0.5 I

The following examples willserve to illustrate several embodiments of the process according to the invention:

Example 1 An iron alloy with 2.2% of silicon was hot rolled in the customary manner to a strip of a thickness of 5.0 The first cold rolling stage was carried out in, 10 passes to a thickness of 1.0 mm. or, in other words, an 80% reduction was eifected. After an intermediate recrystallization anneal the strip was subjected to a further cold rolling stage in 8 passes to effect a 70% reduction to produce a strip 0.3 mm. thick. Thefirst and second cold rolling stages were effected on reversing mills. Directly after the cold rolling the strip was aged for 6 hours at 100 C. and then given a final recrystallization anneal at 1200 C. 99 vol. percent of the strip was oriented in the cube texture.

Example 2 An iron alloy with 1.9% of silicon was hot rolled in the customary manner to a strip 3.8 mm. thick. The first cold rolling stage was carried out in 9 passes to a thickness of 0.92 mm. to efiect a 76% reduction. After an intermediate recrystallization anneal the strip was cold rolled in 6 passes to a thickness of 0.35 mm. (a 62% reduction). The cold rolling in both stages was unidirectional. Directly after the cold rolling, the strip was stored for 10 days at C. and thenaged for 40 minutes at 200 C. by placing it in the oven for the final anneal which had been preheated to 200 C. and after completely reaching this temperature holding the strip at such temperature for 40 minutes. Thereupon the final recrystallization anneal was effected at 1200 C. 98 vol. percent of the strip was oriented in the cube texture.

Example 3 An iron alloy with 0.8% silicon was hot rolled in the customary mannerto produce a strip 4.3 mm. thick. The first cold rolling stage wascarn'ed out in 6 passes to a thickness of 0.86 (an 80% reduction). After an intermediate recrystallization anneal the strip was cold rolled in 4 passes to a thickness of 0.30 mm.f(a 65% reduction). The cold rolling in the first stage was uni- 4- directional and in the second stage reversing. Directly afte g mrleti n 9f i le a s! ro n the strip w s fi t aged for '3 days at 20 C. and then given a final anneal at 920 C., a temperaturewbich precludes a transformation of this alloy. 81 vol. percent of the strip was oriented in the cube texture.

Example 4 An iron alloy with 1.6% of aluminum was hot rolled in the customary manner to produce a strip 4.3 mm. thick. The first cold rolling stage was carried out in 7 passes to a thickness of 1.0 mm. (a 77% reduction). After an intermediate recrystallization anneal the strip was cold rolled in 9 passes to a thickness of 0.1 mm. (an reduction). The cold rolling in both stages was reversing. After completion of the cold rolling the strip was aged for 8 days at room temperature and then given a final anneallat 1300" C. ,vol.. percent of the strip was oriented in the cube texture.

Example 5 Aniron alloyv with 1.5% silicon and 0.5% aluminum was hot rolled in the customary manner to a strip 5 mm. thick. 'The first cold rolling stage was carried out in 8 passes to a'thiokness'of 1.0 m. (an 80% reduction). After'anintermediate recrystallization anneal the strip was cold rolled in 6 passes to a thickness of 0.30 mm. '(a 70% reduction). The'cold rolling in both stages was reversing. Immediately after completion of the cold rolling the strip was given a final anneal at 1200 C. without any intermediate ageing. 76 vol; percent of the strip obtained was oriented inthe cube texture.

held for 4 days at -10 C. and thereafter aged for 1 hour at 200 C., Thereafter it was held for a further 40 hours at '10 C before being giventhe final anneal at 1250? C. 82 vol. percent of the strip thus obtained was oriented in the cube texture.

Example 7 An iron alloy with 2.4% of silicon was hot rolled in the customary manner to a strip of a thickness of 5.7 mm. The first cold rolling stage was carried out in 10 passes to a thickness of 0.8 or, in other words, an 86% reductionwas effected. After an intermediate recrystallization anneal the strip was subjected to a further cold rolling stage in 6 passes to effect a 62.5% reduction to produce a strip 0.3 mm. thick. The first and second cold rolling stages were effected on reversing mills. Directly after the cold rolling the strip was aged for 6 hours at degrees and then given a final recrystallization anneal at 1200 C. 96 vol. percent of the strip wasoriented in the cube texture.

Strips and sheets with cube texture which'were produced according to the preceding examples are preferably employed as core sheets for the construction of transformers. The individual core sheets are stamped from such sheets. They have the advantages that they are easily magnetized not only in the rolling direction but also at right angles thereto. The core sheet can be stamped out as a closed rectangle or as a rectangle with a central crosspiece. These core sheets are suited for two and three phase transformers and can replace the previously usual wrapped core of silicon iron having good magnetic proper-ties only in the rolling direction.

Core sheets with cube texture can also be constructed of separatesheets, which in this case are stamped out in 1., U or M shape and are built into previously wound coils. These core sheets have the advantage that they are easily magnetized in each shank thereof and consequently permit easier construction of transformers therewith than with silicon iron strips which have good magnetic properties in only one direction.

Strips and sheets with cube texture can also be used for electrical machines such as, for example, motors and generators. Core sheets for electric machines with one preferential magnetic direction have hardly any advantage over isotropic silicon-iron. Silicon-iron with cube texture, on the other hand, because of its four fold symmetry, can be very advantageously used in electric four poled machines. In eight, twelve or m-poled machines the sheets with cube texture can upon lamination each be turned 45 or respectively 30 or generally A laminated core constructed in this manner has the desired good properties in the direction of the 4-, 8-, 12- or m poles. The core sheets for larger electric machines may be composed of several single stampings with cube texture.

The advantage in such construction resides in a high density of magnetic flux at the same energizing current in comparison with that obtained with the previous customary isotropic dynamo sheet or silicon iron with only I anneal, the steps which comprise effecting at least a 75% reduction in the second to last stage of the multiple stage cold rolling and effecting at least a 62% reduction in the last stage, the number of passes employed in the last cold rolling stage and second to last cold rolling stage not being greater than and upon completion of the cold rolling subjecting the cold rolled stock to a predetermined ageing for a predetermined period of time at a predetermined temperature before it is subjected to the final recrystallization, the temperature and duration of such ageing being such as to cause an improvement in the quality 2. The process of claim 1 in which in multiple stage cold rolling a reduction between and is efiected in the second to last stage.

3. The process of claim 1 in which the number of passes employed in the last cold rolling stage and the second to last rolling stage is between 2 and 8.

4. The process of claim 1 comprising in addition maintaining said stock at a temperature up to 0 C. during any period of time between the cold rolling and the final recrystallization anneal which is not taken up by the ageing treatment.

5. The process of claim 1 in which said ageing is eifeoted at room temperature over a period of 2 to 10 days.

6. The process of claim 1 in which said ageing is eficcted at about C. over a period of 1 to 10 hours.

7. The process of claim 1 in which said ageing is effected at about 100 C. over a period of 3 to 6 hours.

8. In combination With'a process for the production of a substantial cube on face (100) [001] texture in high quality magnetizable sheets and strips of a high quality magnetizable iron alloy selected fiom the group consisting of iron-silicon alloys containing 0.5 to 2.5% silicon, iron-aluminum alloys containing 0.5 to 2% of aluminum and iron-silicon-alurninum alloys in which the content of silicon-j-aiuminum is from 0.5 to 2.5 in which hot rolled sheets and strips are subjected to single stage cold rolling and then subjected to a final recrystallization anneal, the steps which comprise effecting a 70 to 90% reduction in the cold rolling, the number of passes em- 7 pioyed in the cold rolling not being'greater than 10 and upon completion of the cold rolling subjecting the cold rolled stock to a predetermined ageing for a predetermined period of time at a predetermined temperature before it is subjected to the final recrystallization, the temperature and duration of such ageing being such as to cause an improvement in the quality of the (100) [001] grain orientation achieved upon the final recrystallization anneal and ranging from room temperature for a period of 2 to 10 days to 200 C. for a period of about 40 to 60 minutes, the period of such'ageing being inversely proportional to the temperature employed.

References Cited in the file of this patent UNITED STATES PATENTS Canada June 27, 1950 

1. IN COMBINATION WITH A PROCESS FOR THE PRODUCTION OF A SUBSTANTIAL CUBE ON FACE (100) (001) TEXTURE IN HIGH QUALITY MANETIZABLE SHEETS AND STRIPS OF A HIGH QUANTITY MAGNETIZABLE IRON ALLOY SELECTED FROM THE GROUP CONSISTING OF IRON-SILICON ALLOYS CONSISTING 0.5 TO 2.5% SILICON, IRON-ALUMINUM ALLOYS XONTAINING 0.5 TO 2% OF ALUMINUM AND IRON-SILICON-ALUMINUM ALLOYS IN WHICH THE CONTENT OF SILICON+ALUMINUM IS FROM 0.5 TO 2.5% IN WHICH HOT ROLLED SHEETS AND STRIPS ARE SUBJECTED TO MULTIPLE STAGE COLD COLLING AND THEN SUBJECTED TO A FINAL RECRYSTALLIZATION ANNEAL, THE STEPS WHICH COMPRISE EFEECTING AT LEAST A 75% REDUCTION IN THE SECOND TO LAST STAGE OF THE MULTIPLE STAGE COLD ROLLING AND EFFECTING AT LEAST A 62% REDUCTION IN THE LAST STAGE , THE NUMBER OF PASSES EMPLOYED IN THE LAST COLD ROLLING STAGE AND SECOND TO LAST COLD ROLLING STAGE NOT BEING GERATER THAN 10 AND UPON COMPLETION OF THE COLD ROLLING SUBJECTING THE COLD ROLLED STOCK TO A PREDETERMINED AGEING FOR A PREDETERMINED PERIOD OF TIME AT A PREDETERNINED TEMPERATURE BEFORE IT IS SUBJECTED TO THE FINAL RECRYSTALLIZATION, THE TEMPERATURE AND DURATION OF SUCH AGEING BEING SUCH AS TO CAUSE AN IMPROVEMENT IN THE QUALITY OF THE (100) (001) GRAIN ORIENTATION ACHIEVED UPON THE FINAL RECRYSTALLIZATION ANNEAL AND RANGING FROM ROOM TEMPERATURE FOR A PERIOD OF 2 TO 1/ DAYS TO 200*C. FOR A PERIOD OF ABOUT 40 TO 60 MINUTES, THE PERIOD OF SUCH AGEING BEING INVERSELY PROPORTIONAL TO THE TEMPERATURE EMPLOYED. 